I thought so, I had someone, who apparently breeds anery boas, tell me that she isn't anery. Told me that anerys are black and grey, and lack ALL colour. Which is not even the definition of anerythristic.. anery snakes are generally black and white, but yeah.
She has no red, so I have no reason to believe she is anything else, not to mention I have no idea what else she could possibly be.
Some good anerys start out almost totally greyscale when you look at pics.. and don't show much brown at all, but they get more brown as they age (just like anery BPs). I would agree that yours is an anery. I would have that person show you pics of their ADULTS to compare to.. .I'm sure they have brown in them.